Process for preparing a monoalkyl aromatic

ABSTRACT

AN IMPROVEMENT IN A PROCESS WHEREIN A FIRST COMPOUND IS CONVERTED TO A SECOND COMPOUND IN AN ESSENTIALLY IRREVERSIBLE REACTION OR TO THE SECOND COMPOUND AND TO A THIRD COMPOUND IN ESSENTIALY IRREVERSIBLE REACTIONS AND THE SECOND COMPOUND AND THE THIRD COMPOUND ARE CONVERTIBLE TO EACH OTHER IS EQUILIBRIUM-LIMITED REACTIONS WHICH INVOLVES INTRODUCING THE THIRD COMPOUND INTO THE REACTION ZONE IN AN AMOUNT GREATER THAN THE AMOUNT THAT WOULD BE PRESENT AT EQUILIBRIUM AND TERMINATING THE PROCESS BEFORE THE REACTION MIXTURE REACHES EQUILIBRIUM.

Dec. 4, 1973 N. L. CARR ET AL 3,776,971

PROCESS FOR PREPARING A MONOALKYL .AROMATIC Filed Aug. 13, 1971 4 Sheets-Sheet :3

NORMA/V L. CAR/2 DAN/EL )4 aka Dec. 4, 1973 CARR ET AL PROCESS FOR PREPARING A MONOALKYL AROMATIC 4 Sheets-Sheet 5 Filed Aug. 13, 1971 Dec. 4, 1973 N. L. CARR T AL- PROCESS FOR PREPARING A MONOALKYL AROMATIC 4 Sheets-Sheet 4.

Filed Aug. 15, 1971 w 0 Q 0 9 7 0 0 2 .0 w a A M 0W 7 M 7 s QM 7 0 w 1 w B w w w m m Q 6 am W W 7 7 7 p A flaw 7 ,7 H 7 7 M 7 7 77 u 8 6 M. 2 0 7. 7 4 2 W W 0 w m M m M w 0 & RM mm. lm WM M m N OA/V/EL K C-KO United States Patent M 3,776,971 PROCESS FOR PREPARING A MON OALKYL AROMATIC Norman L. Carr, Allison Park, and Daniel Y. C. K0,

Pittsburgh, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa.

Filed Aug. 13, 1971, Ser. No. 171,474 Int. Cl. C07c 3/52 U.S Cl. 260-671 P 12 Claims ABSTRACT OF THE DISCLOSURE An improvement in a process wherein a first compound is converted to a second compound in an essentially irreversible reaction or to the second compound and to a third compound in essentially irreversible reactions and the second compound and the third compound are convertible to each other in equilibrium-limited reactions which involves introducing the third compound into the reaction zone in an amount greater than the amount that would be present at equilibrium and terminating the process before the reaction mixture reaches equilibrium.

This invention relates to a process wherein there occurs essentially irreversible and equilibrium-limited reactions, illustrated, for example, by the following general reaction mechanism:

n\- o w N wherein each of M, N and O are chemical compounds. In the above, reactions, a reaction mixture containing compound M is converted, in any manner, batch or continuous operation, with or without catalyst, to compound N in an essentially irreversible reaction or said compound M is converted to said compound N and to compound 0 in essentially irreversible reactions. Compounds N and O,

on the other hand, are convertible to each other in essentially equilibrium-limited reactions. During the course of the reactions the concentration of said compound 0 reaches an amount in excess of that amount present at equilibrium before the reaction mixture reaches equilibrium.

In accordance with the process defined and claimed herein, we have found that we can minimize the formation of said compound 0 and, in fact, we can virtually eliminate net production of said compound 0 in said process, as well as reduce the reaction time, and still maintain desired conversions and selectivity to said compound N, by the mereexpedient of adding said compound 0 to the reaction mixture in an amount greater than the amount that would be present at equilibrium and terminating the process before the reaction mixture reaches equilibrium, preferably when the amount of said compound O in the reaction product corresponds substantially to the amount of said compound 0 initially added to the reaction mixture. In a preferred embodiment at the ermination of the process, said component 0 is recovered from the reaction product in any suitable or convenient manner and is recycled.

The reaction mechanisms defined above the merely representative and are equally valid whether or not two or more reactants are employed resulting in the formation of two or more reaction products. For example, procedures such as the reaction of benzene (B) with propylene (P), in batch operation or continuously, to produce a reaction product containing desired cumene (C) and nude:

31,776,971 Patented Dec. 4, 1973 The process of this invention can further be illustrated by reference to the following reaction mechanisms:

k ziten the kinetics of which are postulated as follows: r =k C r =k C r =k C and r =k C In the above, k1, k2, kg and k., are reaction rate constants, r r r and r are reaction rates and C C and C are the concentrations of compounds M, N and 0, respectively, and are assumed to have a dimension of mols per cubic centimeter. A differential material balance was set up for each of compounds M, N and O and the resulting differential equations were programmed on an analog computer. The reactions were assumed to take place either in a flow reactor or in a batch reactor. In a flow reactor time is referred to as residence time and for a batch reactor the time was considered actual time or batch time. Using the values of k =0.0926, k =0.6l5, k =0.O69 and k =0.64, the concentration profiles shown in FIG. I were obtained, wherein concentration in mols of each component per cubic centimeter of reaction mixture is plotted against residence time or batch time in seconds. A simulation study similar to that of FIG. I was made but wherein the initial reaction mixture contained 0.1 mol of compound 0 per cubic centimeter of total reaction mixture. The concentration profiles so obtained are illustrated in FIG. II. It can be seen that the equilibrium concentration of compound 0 is about 0.09 mol per cubic centimeter. Thus, by adding 0.1 mol of compound 0 to the initial reaction mixture, this compound is present in an amount in excess of that amount that would be present at equilibrium. Note that the concentration of the undesired compound O at a residence time (or batch time) of eight seconds is equal to the initial concentration of compound 0. In other words, at this residence time we havevirtually eliminated the net production of compound 0. This can further be illustrated by noting the concentration profile of compound N. At the residence time of eight seconds compound M is virtually completely converted and the concentration of compound N is equal to the initial concentration of compound M. This means that a selectivity of 100 percent has been achieved. Had the reaction been permitted to reach equilibrium, however, it can be seen that a residence time of about 12 seconds would have been required, which is 50 percent greater than that needed in the practice of this invention. While it is true that at equilibrium some additional amount of compound N would have been produced, it would have come from compound 0 and not from compound M. No net production or reduction of compound 0 is desired in the preferred embodiment herein. However, in the situation wherein equilibrium is reached, an additional amount of 7 compound 0 would be needed in order to maintain the 3 enough to permit internal absorption of benzene and not more than 90 percent of their aluminum atoms associated with monovalent cations, for example, sodium or potassium, and the remainder with polyvalent cations, for example, lanthanum, cerium, etc. and/or ammonium or hyducted to determine the rate constant and the associated activation energies so that the kinetic model represented the experimental data. FIG. III, which is representative, contains the concentration profiles obtained from the reaction of benzene with propylene in a molar ratio of drogen. A particularly effective zeolite is zeolite Y such :1 and at a temperature of 214 C., wherein [C is as defined in U.S. Pat. No. 3,130,007. An example of plotted agains liquid weight hour space time (LWHST), zeolite Y will fall within the following chemical composiwherein tion' [C ]=C1/C1 maximum, C C, maximum: mols per 100 grams 56+y[( 2)56+y( 2)136-y 10 of total fluid, C -:2, C =0.25, C wherein generally has a value of 0, but can vary from max1mum= and CD maxtmum= 8 to +20. In the specific reaction herein a Y zeolitic A Simulation Study Similar to FIG III was made but molecular sieve of the following unit cell formula was wherein the molar ratio of benzene to propylene was used: the temperature was 232 C. and the initial reaction mix- (L 031+,) ture contained 0.0064 mol of diisopropyl benzene per A1O2)55 7(siO2) 13m] .ZHZO mol of total feed. The concentration profiles so obtamed are illustrated in FIG. IV. It can be seen that the equiliwhlch been prevlously heated 9 a temperature of brium concentration of diisopropyl benzene in FIG. III about 550 C. for about one hour, w1th, presumably, the is about 0006 mol of diisopropyl benzene per mol of loss of NH;, and H 0 therefrom. A one-half lnch nner total feed. Thus, by adding 0.0064 mol of diisopropyl dlfimeter szfmch long stamless l reactor P benzene in the initial reaction mixture, this compound is wlth a three'lnch by so'mch Jacket filled Wlth dlxyl present in excess of that amount that would be present at ylethane as a heat transfer Fledmm was used- Heat was equilibrium. Note that the concentration of diisopropyl supplied with a calrod electrlcal heater and was controlled benzene at a LWHST of (1084 is equal to the initial com by a thermoelectric controller. A thermowell extended cocentration thereof In other Words at this LWHST We axially through the l'eactor- The temperature in the reactor have virtually eliminated net production of diisopropyl was measured y thermocouples evenly P benzene. This can further be illustrated by noting the the preheat section, catalyst bed and support section. The concentration r fil f propylene and cumene At a pressure was controlled by means of a pressure control LWHST f 0,084 o ylene is virtually completely valve in the effluent Feed to the reactor Was P p verted and the concentration of cumene is equal to the P Y y an adjustable Stroke Proportiohihg P p from initial concentration of propylene. This means that a a callbrated feed tank. The reactor was filled with a prel ti it f 100 pol-cent h b hi d, H d h heat Section of glass heads to a depth of 14 ihches- The reaction been permitted to reach equilibrium, however, it catalyst Section, 13 inches in depth, Was Composed of 10 can be seen that a LWHST of 0.12 would have been regrams of the Specific 10 to 20 mesh Y yp zeolitic 1110166- quired, which is almost percent greater than needed ular sieve catalyst defined immediately hereinabove with in the practice of this invention. tWO Volumes of 8 to 10 mesh quartz P Vohlme 0f the In a typical reaction exemplifying the type of reaction catalyst. The remaining reactor length was filled with glass d fi d nd laim d herein n aro ati o o d can b beads. The efiluent from the reactor was cooled and col- 40 t d with an olefin to obtain an alkyl aromatic, for leCted ill a gas-liquid SePafator- The Off-gas Was e su ed example, benzene can be reacted with propylene to obtain by a wet test meter, while the liquid product was recovcumene as the desired compound and diisopropyl benzene ered and weighed. The results obtained are tabulated beas undesired compound, in a molar ratio of about 1:1 to low in Table I. about 15:1, preferably about 5:1 to about 10:1, at a tem- TABLE I Run Number 500 500 500 500 500 500 500 500 500 500 232 232 214 214 214 214 232 232 232 232 9.96 9.96 9.96 9.96 9.96 9.96 5.905 5.905 5.905 5.905 0. 0498 0.1054 0.0129 0.02525 0.0506 0.0833 0.01262 0.0267 0.0515 0.1 Reactants (mols per 100 grams): 3

Benzene 1.215 1.215 1.215 1.215 1.215 1. 215 1.215 1.1733 1.1733 1.1733 1.1733 Propylene 0.122 0.122 0.122 0.122 0.122 0.122 0.122 0.1986 0.1986 0.1986 0.1986 Product (mols per 190 grams):

Benzene 1.1027 1.10 1.09 1.109 1.1065 1.1036 1.1023 1.066 0.9956 0.9881 0.9810 Cumene 0.10 0.111 0.1128 0.0999 0.1066 0.1075 0.1107 0.1426 0.1655 0.1770 0.1785 Diisopropyl benzene 0.00813 0.00356 0.002 0.0113 0.00849 0.00485 0.0310 0.02409 0.01223 0.00810 0.0073 Propylene 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

1 Liquid weight hourly space time= gram cat alyst hour/grams of total fluid. 2 Mols/IOO grams of total fluid, with total fluid including total reaction mixture.

Based on the above data the following reaction mechanism and kinetics were proposed:

1 Benezene (B) Propylene (P) -v Cumene (0) 2 Benezene 2 Propylene -r Dllsopropyl Benzene (D) Dilsopropyl Benezene Benzene 2 Cumene 'Wherein k k k;, and k; are reaction rate constants,

r r r and r are reaction rates (gram mols per hour .per gram of catalyst) and C 0 C and C are conperature of about to about 260 C., preferably about 200 to about 235 C., and a pressure of about 350 to about 700 pounds per square inch gauge, preferably about 400 to about 550 pounds per square inch gauge, at a LWHST of about 0.03 to about 1.0, preferably from about 0.04 to about 0.5. The amount of undesired compound that can be present at equilibrium can be from about 0.01 to about 0.15 mol per mol of total final product, generally from about 0.03 to about 0.08 mol. In accordance with the procedure defined and claimed herein the amount of undesired compound added to the initial reaction mixture is in excess of such equilibrium amount, for example, from about 0.1 to about 50, preferably from about one to about 30, percent molar excess. The process is preferably terminated prior to the time the reaction product reaches equilibrium, most preferably when the amount of undesired compound in the reaction product is equal to the amount in the initial reaction mixture.

The improvement herein has been both broadly and specifically described and defined, but it is apparent that the same is applicable to any process wherein there occurs essentially irreversible and equilibrium-limited reactions, as exemplified by the general reaction mechanisms defined above, for example, alkylation reactions, such as the alkylation of benzene with propylene or ethylene to obtain cumene or ethyl benzene, respectively, as desired compounds and diisopropyl benzene or diethyl benzene, respectively, as undesired compounds, or the alkylation of toluene with propylene to obtain cymene as the desired compound and diisopropyl toluene as the undesired compound, dealkylation reactions, such as the reaction of toluene with hydrogen at elevated temperatures to obtain benzene as the desired compound and diphenyl as the undesired compound, etc.

Obviously, many modifications and variations of the invention, as hereinabove set forth, can be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. In a process wherein an olefin is converted, by reaction with an aromatic hydrocarbon, to a monoalkyl aromatic and to a dialkyl aromatic in essentially irreversible reactions and said monoalkyl aromatic and said dialkyl aromatic are convertible to each other in equilibrium-limited reactions, during the course of said reactions the concentration of said dialkyl aromatic reaches an amount in excess of that amount present at equilibrium before the reaction mixture reaches equilibrium, the improvement which comprises introducing said dialkyl aromatic into the reaction zone in an amount greater than the amount that would be present at equilibrium and terminating the reaction before the reaction mixture reaches equilibrium.

2. The process of claim 1 wherein the amount of said dialkyl aromatic in the reaction product upon termination of the reaction corresponds substantially to the amount of said dialkyl aromatic initially added into the reaction zone.

3. The process of claim 2 wherein said dialkyl aromatic in the reaction product is recycled to the reaction zone.

4. The process of claim 1 wherein said olefin is propylene, which is reacted with benzene to obtain cumene, diisopropyl benzene is said dialkyl aromatic and said diisopropyl benzene and cumene are convertible to each other in equilibrium-limited reactions.

5. The process of claim 4 wherein the amount of diisopropyl benzene upon termination of the reaction corresponds substantially to the amount of diisopropyl benzene initially added to the reaction zone.

6. The process of claim 5 wherein the diisopropyl benzene in the reaction product is recycled to the reaction zone.

7. The process of claim 1 wherein the amount of said dialkyl aromatic is initially present in said reaction mixture in an amount from about 0.1 to about 50 percent molar excess of the amount that would be present at equilibrium.

8. The process of claim 1 wherein the amount of said dialkyl aromatic is initially present in said reaction mixture in an amount from about one to about 30 percent molar excess of the amount that would be present at equilibrium.

9. The process of claim 4 wherein the amount of said dialkyl romatic is initially present in said reaction mixture in an amount from about 0.1 to about 50 percent molar excess of the amount that would be present at equilibrium.

10. The process of claim 4 wherein the amount of said dialkyl aromatic is initially present in said reaction mixture in an amount from about one to about 30 percent molar excess of the amount that would be present at equilibrium.

11. The process of claim 4 wherein the reactants are benzene and propylene and are present in a molar ratio of about 1:1 to about 15:1, the reaction temperature is about to about 260 C. and the pressure about 350 to about 700 pounds per square inch gauge.

12. The process of claim 4 wherein the reactants are benzene and propylene and are present in a molar ratio of 5:1 to about 10:1, the reaction temperature is about 200 to about 235 C. and the pressure about 400 to about 550 pounds per square inch gauge.

References Cited UNITED STATES PATENTS 2,403,785 7/ 1946 Britton et al. 260-671 R 2,818,452 12/1957 Mavity 260-671 P 2,995,611 8/1961 Linn et a1 260671 R 2,883,438 4/ 1959 Egbert 26067l P 2,920,118 l/ 1960 Landeau et a1 26'0671 P 3,274,278 9/1966 Kapur et a1 260-671 B 3,385,906 5/1968 Kaufman 260671 P OTHER REFERENCES Houqen et al.: Chemical Process Principles, Pt. II, 2d edition, John Wiley & Sons, New York (1954), pp. 1020-1.

CURTIS R. DAVIS, Primary Examiner US. Cl. X.R.

5233 Um'mn STATES PATENT OFFICE CERHFECATE OF CORRECTION December 4, 1973 Patent No. 0 7V6, 971 Dated Inventor(s) Norman L. Carr and Daniel Y. C. K0

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1,, line 62, "ermination" should b "termination'v' Column 1, line 65, "the" should be "are".

Column 3, line 8 of column 11in Table I 190 grams" should be "100 grams".

Column4, line 7, "agains" should be "against" Signed and sealed this 16th day of April l9?l4..

(SEAL) Attest: v EDWARD MJLETGHERJR. L}. MARSHALL DANN Attesting Officer v Commissioner of Patents 

